When conman CaptainJack Harkness planted a Chula ambulance in 1941 London, the Chulananogenes, who had never previously encountered humans, infected a dying human boy named Jamie caught in the London Blitz. Assuming that the gas mask he was wearing was part of his face, they "healed" him, and unintentionally created the "Empty Child," a "zombie" based on Jamie's characteristics and injuries at death. Thus, everyone affected by the plague inherited a gas mask in place of their faces, severe head trauma on the left side, partial collapse of the chest cavity of the right, and a gash on the back of their right hands.

The nanogenes also gave the child the standard abilities of Chula soldiers, specifically super-human strength, telepathic abilities and the ability to communicate using anything with a speaker grill. The Empty Child still had a child-like mentality and escaped to search for its mother.

The Empty Child compulsively searched for his mother, and, in doing so, contaminated other humans with the nanogenes. Those who were infected did likewise so that the nanogenes spread in a fashion similar to a virus. The child, and all victims of it, were infamous for repeating the phrase, "Are you my Mummy?", endlessly. At first, people were only infected if touched by someone who was already infected, though it soon became airborne.